Flange mask



FIG. 1 is a perspective view of a flange mask embodying my new design;

FIG. 2 is a top view thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is a left side view thereof, the back view being identical thereto; and,

FIG. 5 is a right side view thereof, the front view being identical thereto. 

The ornamental design for a "flange mask", as shown and described. 